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Informing women on breast cancer overdiagnosis

In a study exploring women's responses to being told about overdiagnosis in breast cancer screening, most women felt the information was important and could enable them to make choices.

The University of Sydney study, published in the British Medical Journal today, also found that prior awareness of overdiagnosis was minimal and, although it is a complex and unfamiliar topic, most women were able to understand the issue. Providing women with the information may or may not influence their approach to screening, depending on the extent of the overdiagnosis and individual preferences.

"Currently around 1.7 million women are screened every two years for breast cancer in Australia and, as in other developed countries, hardly any information on overdiagnosis is provided," said lead author Jolyn Hersch, a PhD candidate at the University of Sydney's School of Public Health.

Overdiagnosis or overdetection is where a screening mammogram detects a cancer that would not have caused death or presented clinically during the woman's lifetime.

"The study aims to inform effective strategies for communication about overdetection to women considering screening."

It is important to note that while a majority of women in the groups expressed interest in being better informed about screening, many also wanted continuing encouragement to have screening.

"Also worth noting is that for some participants the information did not cause uncertainty about whether to be screened for breast cancer. Instead the uncertainty was about whether to have the standard treatment for a screen-detected cancer or whether they should consider alternative approaches to treatment."

The qualitative study used focus groups to inform 50 women aged 40 to 79 from a range of socioeconomic backgrounds about overdetection of cancer.

"Overdetection and the resulting overtreatment of an inconsequential disease are considered the most serious and important harms associated with early detection of cancer through screening but at this stage pinpointing what level of overdetection occurs remains a challenge," said Hersch.

Several recent studies have estimated an overdetection rate of between 19 and 35 percent, but estimates in other studies have been substantially lower or higher.

"Our study presented women with a range of estimates. At the highest estimate we presented (50 percent) some women said they may think twice about screening, whereas the lower (1-10 percent) and intermediate estimates (30 percent) had limited impact on women's enthusiasm for screening."